Cellulose is a large polysaccharide which comprises D-glucose formed by β-1,4-glucanase and is the main ingredient of a plant cell wall. Cellulose is a natural polymer which exists in great quantities on the Earth, and its carbon content accounts for more than 50% of the carbon content of the plant kingdom. Plants make use of the carbon dioxide in the air by photosynthesis, and then store the chemical energy of carbon dioxide in the bonds of cellulose molecules. Hence, the effective decomposition of cellulose and conversion of its energy and carbon source into energy accessible to human beings will provide a solution to the current food crisis and energy crisis facing humankind nowadays.
Conventional methods for use in processing cellulose fall into three categories, namely chemical processing, physical processing, and cellulase-based decomposition. Cellulase is a composite enzyme composed of multiple hydrolases, and it is produced by fungi, bacteria, and actinomyces in nature. Insoluble cellulose is usually decomposed into monosaccharides for use as a carbon source during a biotech manufacturing process. Cellulase, which degrades cellulose, is available in three types and functions according to its enzyme commission (EC) number as follows: (1) endo-cellulose hydrolase (EC 3.2.1.4; endo-β-1,4-glucanase) cuts the β-1,4 glucanase in the cellulose molecule at random and releases cello-oligosaccharides to thereby increase the number of reducing ends and decreasing viscosity; (2) exo-cellulose hydrolase (EC 3.2.1.91; exo-β-1,4-glucanase) cuts cellobiose from the highly crystallized terminal end of cellulose; and (3) EC 3.2.1.21; β-1,4-glucosidase hydrolyzes cellobiose to produce glucose.
The enzymatic activity of exo-cellulose hydrolase is inhibited by the feedback from its product—cello-disaccharides, and the presence of β-1,4-glucosidase is conducive to the prevention of excessive accumulation of cello-disaccharides and thus the reduction in its feedback inhibition of exo-cellulose hydrolase.
Conventional commercially available cellulases are produced mostly by Trichoderma species or Aspergillus species. Although Trichoderma secretes a huge amount of end-cellulose hydrolase and exo-cellulose hydrolase, its β-1,4-glucosidase demonstrates relatively low enzymatic activity and thus is likely to cause the accumulation of cello-disaccharides produced during the process of enzyme-based hydrolysis of fibrous biological matters, thereby bringing about feedback inhibition and thus deteriorated efficacy of hydrolysis. As a result, it is necessary to overcome the aforesaid drawbacks by including the β-1,4-glucosidase produced by Aspergillus. 
Accordingly, it is imperative to perform co-cultivation on two different strains, namely Trichoderma and Aspergillus so as to produce their cellulases by induction of cellulose and lactose and thus enhance the enzymatic activities of their cellulases.